This invention relates to liners or inflations for teat cup assemblies of vacuum-operated milking machines and, more particularly, to such inflations including a head end which fits over the upper end of a teat cup shell and includes a central opening for receiving a cow's teat.
Automatic milking machines employ teat cup assemblies including a hollow, rigid outer shell which is attached to a pulsating vacuum line and a resilient, tubular liner or inflation installed in the shell in a manner to form a seal at both ends of the shell. A cow's teat is inserted in the upper end of the inflation and the lower end is connected to a so-called claw of the milking machine. During the milking operation, the teat cup assembly is suspended from a cow's teat, primarily by the engagement between an opening or mouth in the upper or head end of the inflation and the cow's teat and milk flows through the inflation under the influence of a vacuum maintained in the milking machine claw.
One type inflation has a head end including a downwardly extending cuff which fits snugly over the upper end of the shell and a generally horizontally extending end wall having a circular central opening for receiving a cow's teat. One problem with this type inflation is a tendency for the shape of the mouth to be distorted (out of round) at the time a teat is inserted and/or during the milking operation. A misshapen mouth permits undesirable amounts of air to enter the inflation during milking, resulting in excessive vacuum loss, slurping, inflation slippage or dropoff. This undesired distortion of the mouth can result from the end wall being deflected either inwardly or outwardly from its normal horizontal or flat position when a teat is inserted and/or during the milking operation. It also can result from the material surrounding the mouth being so elastic that the opening can be pushed sideways by a cow's teat.
Representative prior constructions for milking inflations known to applicant including features which might at least partially alleviate the above problem are disclosed in U.S. Pat. Nos. 3,659,557 (Noorlander), issued May 2, 1972; 3,696,790 (Albright) issued Oct. 10, 1972; 4,116,165(Arrington) issued Sept. 26, 1978; and 4,141,319 (Maier et al.), issued Feb. 27, 1979.
The Noorlander patent discloses an expansion-ring type inflation with the teat-receiving portion including a plurality of longitudinally extending corrugations which cause a central opening having an unreinforced edge to be undulated. The Arrington patent also discloses an expansion-ring type inflation and the teat-receiving end portion includes a tapered wall and a bead surrounding a central opening. In expansion-ring type inflations, a substantial stretching of the material forming the teat-receiving portion by the expansion ring tends to keep the resulting diaphragm in a horizontal position.
FIGS. 13 and 16 of the Albright patent illustrate an inflation having a teat-receiving portion including a plurality of radially extending corrugations and a circumferentially extending corrugation which respectively spread and squeeze when a teat is inserted into a central opening having an unreinforced edge. FIGS. 4 and 5 of the Maier et al patent illustrate an inflation having a a plurality of radially extending ribs. These ribs serve to support the radial tension applied on the unreinforced edge of a central opening, but terminate short of the opening so that the front edge of the opening is particularly elastic and, therefore, subject to distortions.